The present invention relates to device for moving a member linearly, which is adaptive for vertical driving of a pen of an X-Y plotter, drafter or the like, i.e. a linear actuator.
A system for a driving a pen using a plunger solenoid is known as means for controlling a pen of an X-Y plotter. In this system, it is difficult not only to reduce the impact at contact of the pen with a recording paper but also to adjust the pressure of the pen against the recording paper.
In order to eliminate disadvantages as above described, in "HEWLETT-PACKARD JOURNAL" published on November 1981, "Y-Axis Pen Handling System", a system using a magnet and a voice-coil was disclosed by Robert D. Haselby et al. This system includes a position sensor for a pen, and enables the control of the coil current corresponding to the position of the pen and therefore performs pen-lift control smoothly and rapidly. However, this reference discloses only a system for detecting the position of the pen optically using a light-emitting-diode (LED), a phototransistor and a position sensor flag, but not system for detecting the pen position and speed by magnetic means.